U.S. Publication No. 2006/0197371 discloses a vehicle wheel disk having an axially outwardly extending rib or protrusion at a position located radially inside a vent window, as shown in FIG. 4 thereof.
More particularly, in FIG. 4 of U.S. Publication No. 2006/0197371, the rib extends in a radial direction of the wheel from a first portion to a second portion. The first portion is a vent window surrounding curved portion which is located radially inside the vent window and is curved axially inwardly. The second portion is a portion located radially inside a ring region where hub bolt holes are provided. In a cross section of the wheel taken along a plane perpendicular to an axial direction of the wheel, the rib has a pair of side walls and a crest wall that connects ends of the pair of side walls and has the configuration of a convex arc with a single curvature.